Boileb



J. DOHERTY.

BOILER CONSTRUCTION.

APPLICATION FILED SEPT 20, 1917- 1,402,843. Patented Jan. 10,1922.

2 SHEETS-SHEET 1.

Jcunea Doll/6kg J. DOHERTY.

BOlLER CONSTRUCTION.

APPLICATION FILED SEPT 20,1917.

Patented Jan. 10, 1922.

2 SHEETSSHEET 2.

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a 11v VENTOR BY a f v A TTORNE Y BOILER tltlllllhTHUflTION.

Application filed. fieptcmher T 0 all whom it may concern;

Be it known that l, dairies Dornurrr, a citizen 01" the United, iritates, residing at llhicage, in the county of Cool: and State 0:.Illinois, have invented certain new and. useful Improvements in BoilerConstructions; and I do hereby declare the flEOllOWillg to he s :tull,clean and erect description of the invention, such as will ensble othersskilled in the art to which it appertains to make and use the same.

This invention relates to coal hurninp; tun naces for steam or hot Waterheating, and like uses and more particularly to that type of suchfurnace in which an. overhead sup ply of supplementalcombustion-supporting air is admitted to the fire-hon for perfecting thecombustion reuctioin thereby rendering such furnaces capable oil?operation on bituminous coal Without objectionable srnolr and hence withcorresponding thermal eficiency. The type of furnace referred to isWellknown in this art and many ditlerent :t'orins oi it have beenheretofore disclosed in pet ents but none of them, so far a I am awarehas resulted in a furnace equipment suited to the demands oi? the trade.or capable of the continued efficient service as I here di coveredispossible and practical by the or ganizetion of means hereinaitterdisclosed.

My invention consists in the manner or": in troducing and heating theSUPlDlQlYl-Eri al air and in the structure of the air supply duct andits air distributing: orifices and in the relation oi such orifices tothe fuel bed and the path of. the fire erases as well in theorganization or? these features in the structure of sectional furnaces,all as hereinafter more fully described In the eccompainyin drawing.illu" the preferred form oi the inventioin K 1. is perspective of asectional Water-heatinp; furnace with the side wall brolren. out and theinterior parts shown in vertical and oblique sections.

Figure 2 is a partial face view of the water-curtain section.

Figure 3 is an enlerpged cross-section of the Water curtain, and

Figure 4 a detail showin a portion of the exposed or air-heatine Well.of the air duct.

The furnace illustrated comprises front and rear Water-containingsections 1 and 3 and a series of intermediate watercontein inn; sections2, all having: the same external contour and adapted to he clampedtightly Specification of Letters Patent.

Patented Jan. Ht, 192%.

isaa'ri.

together, as usual in sectional idirnaces so that the Writer spaces ine: ch section are put in coini'nunication, and the assembled sec tions"form the walls of the fire hex and the usual tlue spaces by means oi?which the reouisite surface is atlordec for transfer of from the tirecases to the Water. For us purpose, the sections constitu..'ng the irontpart of the furnace are provided with cross chambers 2 which aredesirably T- shaped in cross-section. and form the root or crown of thehex. The furnace section new? in rear ot t ese crown. sections, isprovided With a Water-containing; cross member or bottle of considerablevertical dimension so that it depends Well below the crown Wall endterms a Water curtain. marking" the rear limit ot the upper part of thethe box. The means for admitting the supplemental air is associated withthe lower edge out this Water curtain as presently explained. The crosschainliier members Q of the turnace sections it in rear of the watercurtain are spaced ore each other forming: lue speces hetween in throughwhich th re oases rise to the upper iorizontal side lines 4 above thefire n t. ln these side 'tlues gases flow itorweirdly ove the crown Well2"; indicated the arrows and then turn and pass rear. h the horizontalcenter flue 8, l and chirnneu not shown. This t is no different from funlone in. common use and is. the preterred although no; a. necessaryarrangement or the tines oi the o ontion.

resent in;

The bottom of the :lirehoi: is formed by a peri orote updraft grate (lwhich is parallel 7 With the crown well and substantially horizontal.The grate extends to the rear ot' the water-znirtain D and ahuts againstor terminutes adjacent to. an uprinht Well B which constitutes anordinary bridge Wall in the 'ueseut case; its function is merely that ofa rctainino Wall tor the bed ot fuel on the grate. The upper front edgeof this Wall is shown in the drawing); beve led and the H The coal issupplied through the feed grate in the usual way and this constitutesthe main supply of combustion-supporting air. The space in rear of thewall B when that is a bridge wall as shown, serves merely as part of theline space or as a chamber tor the collection of dust.

The lower edge of the water-curtain l) extends transversely andhorizontally over the rear part of the grate and :tuel bed, occupying alevel which is somewhat nearer to the grate than to the crown wall 2,and in this position, it cooperates with the fuel bed'clirectly belowit, to form therewith a somewhat restricted passageway throat thror glwhich the lire-box opens into the flue space in rear. Practically all ofthe fire-gases developed in the furnace flow through this passage whichextends across the furnace with practically uniform vertical dimension.The duct A toradmitting the supplemental air is coextensive with thewater-curtain, being substantially coincident with its said lower edgeand receives air from atmosphere, through appropriate, damper controlledinlet openings 6 in the side legs of its furnace section shown in Fig. 2and discharges and distrilnites such air through a series of uniformlyspaced and downwardly directed exit orifices openinq from the lower sideof the duct and theretore'toward the fuel bed. The air flow into andthrough the duct and its orifices is caused by the chimney suction whichsutfices to produce a vigorous discharge through the row of orificesbecause the air path through the grate is more or less ob structed bythe fuel and there is no other equivalent entrance for air to theinterior of the furnace, besides which the location of the duct isnearer to the chimney than other points in the lire-box. The singlecross-duct supplies all the air that is needed for combustion which doesnot enter by way of the grate and supplies it at suliicient velocity tocause it to penetrate the throat passage above mentioned and seeminglyto impinge against the subjacenl; bed of fuel creating an extraordinarymixing effect and turbulence in the tire gases at that point. which ismanifested in practical operation by the de velopment of a sheet oflivid white flame extendino; directly from the water-curtain through thehorizontal lines of the furnace T his effect is in part the result otthe arrangement of all the air duct orifices in a single transverseplane or zone over the rear part of the Fuel bed and distinguishes myinvention from that class 0t supplemental air furnaces in which thesupplemental air is introduced through many separated orificesdistributed over the whole area of the roo orj sides olthe firebox, aswell as from other designs in which supplemental air is admitted withoutadequate velocity or from orifices too remote from the fuel bed producethe necessary turbulence. Bees admitting the supplemental an in the andat the requisite velocity,

men oncounte the lire gases and .l have a ad that unless lt exceeds acertain cr temperature, its ellect on the cllicicnc c the combustionprocess will be ii' uind he generally neutral or actually I have furtherascertained that critical temperature is not attained hen he air duct isenclosed in water or clteted: in such arrangements the thi oucgh the.duct cdiuiotexceed rely low temperature oi the water 1 and that is muchtoo low to produce Mot-ion rcterrcd to and cannot give the ioncl'licienc v r-rhicli is the object of V 7'. cation. in the other hand.l have -o demonst ted, that any material incso oi the air temperatureabove said al point is not attended with any cor ouch: benelit to thereaction and is arc'lorc not nec sary, besides which the oi such hi htemperaturcs involves serious diliicultics on account of the rapiddisint ratimi by the heat oil the material h the air duct is formed. Thedesc ibed location of th air duct, close over .c rear part of the luv]bed. is th hottest mace and so b: as T am aware v V .ractory materialcommercially c, .i ll at can peruizuiculily witbstaml such tcni'eraturc. Previous clliorts to construct ducts in. or near this location.out ol. various kinds of firebriclr have been nosucccss ul on thisaccount and the attempt to remedy the diiliculty by jMlHIltl'lIlSl alarger volume of air through the duct. so a, to lmep the tcnipemturenoun. is not practicablc. because an such air flow as would be ell w 'votor this purpose robs the Fuel pit air supply and thereby he primarycombustion.

these dillicult cs. One oil'- the walls (l of the air duct is arrangedso s to be oirectlv oxaposcd tor substai'itiully the whole of its lengthto the radiant heat of the fuel bed which. as stated, is very intense atthis point. and said wall is thereby highly and also un formly hcatcdand transmits its heat to the air flowing inside the duct. The other oropposite w: ll of the duct is shielded 'l'l'oiu the radiant heat andprotected :urainst :la' quiring' so high a temperature by virtue oi itsproxim ty to the water in the curtain l).

the temperature ol which is of course at all times relatively very low.This side of the duct is therefore kept relativcly cool. Theprotectioi'i and cooling: elliect ol' tlzc water supplemented by thecooling eh'eet ol' the 1 ,aoas ia incoming air, is found in practice tokeep the exposed wall C at such. temperature as to renderit indefinitelyimmune from thermal. deterioration, while the air flowing behind itacquires a temperature high enough to adapt it for immediate chemical.com" mation with the firegases in ordinary c" tion, and to produce thecharact efficient flame effect above referred to. such organization andpartial protection and cooling of duct otherwise highly heated for itsfull length, its combustion-perfecting function is made available in thefullest degree.

The preferred air duct passage as shown in the drawing is formed in partby the metal wall of the water-curtain itself, which is provided alongits lower edge with a series of forwardly projecting teeth It, all ofsubstantially equal size and containing water, and in part by theseparately made wall member C above referred to, which is of angle-barcross section and seated upon the tips of the teeth, as indicated inFigure 3, thus forming the duct passage A. with the spaces between theteeth forming the downwardly directed air orifices. The said spaces areabout the same width as the teeth so that the air is delivered asclosely adjacent and also uniformly spaced, jets or blasts.approximating the form of a continuous sheet of air. The wall U, beingstructurally separate from the water-curtain wall and longitudinallycoextensive with and also being supported intermediate of the ends ofthe duct upon the water curtain, besides having a simple cross-section,is entirely free to expand and contract under thermal change withoutinjury to itself and without imparting strain to the metal of thewatercurtain proper, while neverthless sulfici as stated to establishthe requisite tempt ture in the supplemental. air. While I am not ableto give the exact value of the critical air temperature which itmentioned above, because of the difficulty of ineasuri m it, it will besufficient to those skilled in this art to say that it is attained bysubstantially the extent of wall exposure to the radiant pass off withthe flue gases without miningor sufficiently combining therewith.

In connection with the statement above made that the air duct providesfor the introduction of all the combustion supporting air except thatwhich enters through the grate, it will of course be understood that inevery furnace there is inevitably more or less air leakage especially atthe feed door, and that the feed door may be provided, as in the presentcase, with an air damper for controlling the entrance of outside airabove the fuel. th'dinarily, the effect of air admission thorugh suchdar :r is to chill or suppress the comb" ton rathu than otherwise, suchdampers being princ pally useful when the fire is banked. llnder certainconditi ns and w'th. certain lrlnds of coal a limited admission of airat the feed door may serve to support conituistion, but in any event theamount of air leakage, if any, and the amount admitted through the feeddoor damper, is relatively negligible as respects its effect on the flowthrough the cross duct, so that it does not deem the entering velocityof the latter and the mixing effect which is dependent thereon, and itis therefore true that the said duct and the ash pit together admitsubstantially the whole supply of the combustion support ing air.

The firebox side of the water-curtain above the air duct is faced withrefractory material represented in the present case by tiling 5; thisrefractory surface becoming highly heated is found to lend assistance tothe combustion in the fire-box-possibly by the so-called regenerativeeffect. The water,- curtain is also formed with one or more smallapertures E in its upper part adapted to cause a slow withdrawal ofgases from beneath the crown wall and for the purpose of insuring thecontinuous presence of very hot gases contiguous to said wall so as toutilize their heating effect in the crown wall. water.

Claims:

1.. in a furnace of the type described, the combination with a fire-boxhaving a horizontal, perforate updraft grate and a main air supplythrough the grate, of a transverse baffle wall containing water andcoactinp; with the rear part of the fuel bed on said grate to formtherewith a. throat passage, means for admitting supplemental heated airto the fire-gas flow in said passage com-- prising an air ductassociated in parallel. relation with the lower edge of said wall,

one side of said duct being exposed to the radiant heat whereby it heatssaid supplemental air, and the other side being shielded therefrom and.subject to the coohn effect of the water in said wall, and meansconstituting the exit from said duct adapted to direct said heated aircrosswise of the flow through said passage, said air duct exit and mainair entrance being correlated to produce a velocity of said heated airflow adapting it to mix with said fire-gas flow.

2. In a furnace of the type described, the combination with a fire-boxhaving); a horizontal, perforate updraft grate constituting an entrancefor some of the combustion supporting air, of an entrance forsubstantially all the balance of the combustion supporting airconsisting of a transverse air duct extending directly over and spacedabove burning fuel bed at the rear part of said and forming with saidbed the principal gas flow passage from the fire-box, said duct beingassociated with means whereby it is protected by water on one sit e andsubject to the radiant heat of the combustion on another side, wherebythe. air iow therein is heated, and provided with downwardly di rectedexit means adapted to cause ininture of said heated air with the flowingthrough said passage.

3. In a furnace of the type described., the combination of fireboxhaving a ho tal, perforate updraf crate constituting; an entrance forsome 0 the combustion supporting air and an entrance for substantiallyall the remainder of the supply of comb-uslion-supporting aircomprising; a row of air orifices extending transversely over and at auniform distance above the whole fuel bed at the rear part of said erate and air duct for conducting the air to said .ces 90H? prising; awall having means spaced above the fuel bed for protecting it by water,and another wall uniformly subjected to the radiant heat of thecombustion and serving to heat the air issuing from said orifices.

4. In a furnace of the type described, the combination with a fire-boxhaving; a perforate updraft grate constituting an entrance forcombustion-supportine air, of a transverse fire-loox wall containing;water disposed over the rear part of the fuel bed on said grate, meansfor admitting substantially all the rest of the combustion-supportingair to the fire gas flowing between said wall and fuel bed, comprising atransverse air duct situated directly in front of the lower watercontaining edge of said wall, one side of said air admittingmeans beingexposed to the radiant heat of the combustion and the rear side thereofbeing shielded therefrom and subjected to the cooling-effect of thewater in said wall, and means for directing the heated supplemental airtoward the fuel bed and adapted to cause the same to mix with the firegas fiow beneath said wall.

' 5. In a furnace of the type described, the combination with a fireboxhaving; a perforate updraft grate constituting the main air supply, of atransverse firebox wall containing water and having its lower edgedisposed directly over the rear part of the fuel bed on said grate andnearer to the (gratethan to the firebox roof, means for admittingsupplemental air to the fire flow beneath said wall comprising atransverse air duct associated in parallel relation with said loweredge, one of the walls of said duct being exposed to the radiant heat ofthe combustion and another being shielded therefrom and subjected to thecooling; effect of the water in said wall, and a row of air exitorifices in said duct arranged to direct heat ed air j fl the fuel bed,said main and suppleinentzu air ci'itranccs constituting substantiallythe whole supply of comljuistion supporting" air to the lire-box.

6. in a furnace of the type describml, the combination "ith a fireboxhaving a hurl :aontal perforate updraft grate and a main air supplythrough the grate, of a transverse water-curtain forming the r rboundary wall of the fire-boat, means rm. admitting heated supplementalair to the tmssagrc ben-ath said water curtain comprising an air ductassociated with the lower ed c of said curtain and partly protectedtl'icreby :1 5.Iul115-3 the radiant heat and having; an uir-heatingrwall directly exposed to the radiant heat and an exit adapted fordirecting the heated air from said duct toward the grate.

7. In a furnace of the type described. the combination with a fire-boxha ing a horizontal, perforate up-draft grate and a main air supplythrough the 1:lflllQ, of a supplemental air admission duct disposedsubstantially horizontally and transversely over and out of contact withthe rear part of the burning fuel bed on said grate and providingfire-gas passage betwcen the same and said bed, said duct being formedby trans verse wall members, one of which is waterprotected and one ofwhich is subject to the radiant heat of the combustion and havingdownwardly directed exit means adapted to discharge highly heated aircrosswise into the fire-gas flow through said passage.

8. In a furnace having a horizontal, perforate rip-draft grateconstituting a main air supply, a supplemental airsupply comprising); atransverse air-distributing passage disposed over the rear part of thefuel bed on said grate and open to atmmqahore at the side of the furnaceand constituted of separate passage-forming; wall members, means forkeeping water in contact with one of said passage forming wall members,the other member being directly exposed to the radiant heat of thecombustion whereby it transmits heat to said supplemental air, saidpassage having air exit means directed toward the fuel bed.

9. In a furnace having a horizontal updraft perforate grateconstitutiim' an entrance for pa "t of the combustion-supporting airsupply, an entrance for substantially all the rest of said air supplycomprising" a transverse, substantially straight. air-distributingpassage composed of separate passage-forming members, means for lrcopingwater in contact with one of said passage forming wall members, theother member being exposed to the radiant heat, and both of them beingdisposed directly over the fuel bed, and the passage formed therebyhaving inlets from atmosphere through the sides of the furnace, inalignment with said passage, and having downwardly direct l air-exitmeans,

10, A furnace of the type described. coinprising the combination grate,a wat :urtain located above the fuel bed on said grate and provided irejecting teeth, and a separate member co-acting with sane water-curtainto form an air pas: said passage having entrance means for an: thespaces between said teeth serving 0m distributing outlets from saidpassage.

11, line furnace of the type described, the combination with a grate, ofa transverse, water-containing baffle wall located. above the fuel bedthereon and. forming the rear of the fire-box space, and a separatemember mounted on said wall and forming therewith a supplemental airadmission duct havair air exit means.

12. In furnace of the type described, the combination with a grate, ofwater-con taining member provided with toothlilre projections a memberof angled crosssection supported by said projections and formingairsdmittinpand a'ir-distrib uting passage,

13. In a furnace of the type described, the combination with a grate anda transverse water-cur ain forming the rear wall of the firebox spaceand a sep ately formed member supported lIllJGliIlQ etc of its ends onsaid water-curtain anr ,ssociated therewith to form an air-admittingand. air-distributing cross duct exposed to the radiant heat on one sideand protected by the water in said curtain on another side.

14. In a sectional furnace, the combination with front, rear andintermediate water-containing SEC'tlOlT-l all made of similar externalcontour and assembled to form the furnace body with internal chant bersconstituting fine and lire-box spaces, of means carried by one of saidintermediate water-containing sections constituting a de pendingWater-containing fire-box wall and also constituting an air-coinluctingand distributing passage, said. passage extending crosswise of thefurnace above the fuel bed and having an opening to atmosphe-P at itsend intersecting the side of said intermediate water-containing section.

15. In a sectional furnace of the type dcscribed, the combination with aseries of front watencontaining sections all of similar external.contour assembled. to form the front part of the furnace containing afirebon space and having an up-draft grate, of a water-containin sectionof similar external contour assembled in rear of said front tire boxsections and carrying a depending tran verse water-containing wallsituated over the rear part of said grate and a transverseair-distributing passage located above said grate and directly in frontof the lower portion of said water-containing wall external L l Wall-eare part of the 1.

id, in a sectional 'l' n scribed, the conibinu'. wliter-containing lionsall of similar ex:- ternal contour assembled to fin-n1 the front part ofthe furnace and containing and forming a crown wall with horinontal fluespaces above it and a fire-box. space beneath it, and for said space, ofan intermediate water-containing and ill ila-s ing section of similarexternal contour assembled in rear of said series and having its waterspace extended downwardly to form a water curtain depending below saidcrown wall and over the grate, air-admitting and air-distributing crossduct having down wardly directed air exit means, the walls of said ductbeing supported intermediate of their ends on said intermediate or watereurtain section and another water-containing section or sections alsohaving a similar external contour assembled in rear of saidwater-curtain section to form the rear part of the furnace.

17. in a sectional furnace of the type de scribed, i'vhecombination witha series of front water-containing sections, all of similar externalcontour, assembled to form the front part of the furnace and containinga crown wall with flue space; above it and a fire-box space beneath it,of a watercontaining and flue-forming section in rear of said series,means wholly carried by said last named section constituting atransverse water-curtain depending below said crown wall and alsoconstituting an air-admitting and air-distributing cross duct adjacentthe lower edge of said water curtain.

18, in a furnace of the type described, the combination of a lire-box,updraft grate, constituting the main supply of coinbustion-supportingair, a transverse wateri 0 ill containing baille forming the rear wallof said lire-box having an air duct associated with its lower edgeadapted to deliver substantially all of the balance of the air requiredfor combustion into mining relation with the fire gases passing beneathsaid baths and also having a facing of refractory material on its frontsurface.

19. A sectional furnace of the type described composed of a front, arear and several intermediate vi tor-containing sections, all similarexternal contour and all sseniblcd together to form the furnace withinternal parts constituting flue spaces and a fire bOX, and an updraftgrate constituting the main air supply to the fire box, in comh a seriesof bination with a supplemental air admission duet adapted to introduce.substantially all the balance of the air required for combos tion anddisposed substantially horizontally and transversely over and out ofcontact with the rear part of the burning fuel bed on said grate, andproviding an open firegas passage between itself and said fuel bed, saidduct being formed by transversely extending wall nieinhers, one of whichis oonstituted by a water-containing part of one oil said intermediatel'urnaee+eetions and one of which is constituted by a horizontallyextending member associated with said intermediate section and subjectto the radiant heat of the combustion, said duct havingdownwardly-directed air exit means adapted to discharge the highlyheated sup 'ilemental air crosswise of, and into mixing relation with,the tire-gas flow through said passage. 20

In testimony whereof I afiix my signature.

JAMES DOHERTY.

